Burnishing tape and method of manufacturing the same, and method of burnishing magnetic disk

ABSTRACT

Disclosed is a burnishing tape, a method of producing the same and a method of burnishing a magnetic disk with which a surface of the magnetic disk may be smoothed while contamination of a magnetic disk caused by crushed abrasive grains is prevented. A burnishing tape ( 1 ) manufactured by the method of manufacturing of the burnishing tape according to an embodiment of the invention is used to burnish the magnetic disk. The method includes: kneading and dispersing abrasive grains ( 5 ) and a binder ( 6 ) to prepare slurry; applying the slurry on the support ( 2 ) to form a coating layer; curing the coating layer to form an abrasive grain layer ( 3 ); and forming a liquid lubricant layer ( 4 ) on a surface of the abrasive grain layer ( 3 ).

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority of Japanese Patent Application No.2008-172598 filed Jul. 1, 2008, the content of which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a burnishing tape used for polishing asurface of a magnetic disk used in, for example, a hard disk device, amethod of manufacturing the same, and a method of burnishing themagnetic disk.

2. Background Art

Recently, data is recorded on a magnetic disk in a hard disk device withincreasingly higher density. A recording head is spaced from a magneticrecording surface when moved with respect thereto. The surface of themagnetic disk should be fairly smooth in order to reduce the distancebetween the recording head and the magnetic recording surface.Accordingly, in the manufacturing process of the magnetic disk, after amagnetic layer and a protective layer are formed on a nonmagneticsubstrate, a surface of the outermost layer is burnished with aburnishing tape so as to remove bumps formed or deposited on thesurface.

Burnishing is conducted using, for example, a burnishing tape having analumina coating material applied thereto. The burnishing tape is pressedagainst a medium surface by a rubber contact roll so that the mediumsurface is polished lightly. Since any abnormal bumps on the mediumsurface may be removed during the burnishing process, the distancebetween the recording head and the magnetic recording surface may bereduced in a hard disk device (see, for example JP-A-11-277339).

An exemplary burnishing tape (i.e., a burnishing tape) used in theburnishing process may typically be a tape which includes a polyesterbase film having an abrasive layer formed thereon. The abrasive layer ismade to contact and slide against the surface of the magnetic disk atthe side of the magnetic layer. With this process, fine dust adhering tothe surface of the magnetic disk is removed and the surface is polishedto remove the abnormal bumps on the surface. In this manner, the surfaceis smoothed. Examples of the abrasive may include particles having anaverage particle diameter of about 0.05 to 50 micrometers. Namely, theabrasive may be particles of chromic oxide, α-alumina, silicon carbide,nonmagnetic iron oxide, diamond, γ-alumina, α,γ-alumina, fused alumina,corundum and synthetic diamond (see, for example, JP-A-09-054943).

JP-A-2001-079774 discloses, regarding a polishing film for burnishing ahard disk protective layer, covering the surfaces of abrasive particleswith a coating agent in order to prevent transfer of ionic impuritiesfrom a polishing film to a surface of the hard disk protective layer.JP-A-9-85628 discloses increasing the polishing force of a burnishingtape and preventing scratching generated on a polishing surface byproviding a ceramic coating layer on a surface of the burnishing tape.

SUMMARY OF THE INVENTION

Burnishing of a magnetic disk is typically a process of polishing asurface of a magnetic disk using a burnishing tape. In particular, anabrasive grain surface of the burnishing tape is pressed against asurface of the magnetic disk at the side of a magnetic layer while themagnetic disk is being rotated. In this manner, the magnetic disksurface is polished to remove bumps and thus the magnetic disk surfacemay be smoothed.

The burnishing tape is extended between a feed reel and a take-up reel.The burnishing tape is sequentially supplied from the feed reel and istaken up by the take-up reel. In the course of the burnishing tape beingmoved from the feed reel to the take-up reel, a surface of theburnishing tape opposite to the abrasive grain surface (i.e., a backsurface) may be pressed by, for example, a rubber backing roll or a feltpiece such that the polishing surface of the burnishing tape may bepressed against the surface of the magnetic disk. The burnishing tape issupplied from the reel. The used burnishing tape is taken up andcollected by another reel.

Recently, data is recorded on a magnetic disk with increasingly highdensity. To increase the recording density, the distance between themagnetic head and the magnetic disk is reduced. Now, contamination ofthe magnetic disk surface during the burnishing process has become aproblem.

According to the study of the present inventors, it has been found thatcontaminant of the magnetic disk surface contains alumina particles,which are produced during the burnishing process. In particular,abrasive grains are separated from the burnishing tape or crushed toproduce the alumina particles contained in the contaminant. Moreparticularly, it has been found that, when the magnetic disk surface ispolished to remove the bumps formed thereon during the burnishingprocess, the abrasive grains adhering to the burnishing tape areseparated or the surfaces of the abrasive grains are crushed (i.e.,split) slightly and the separated grains or the abrasive grain powderproduced by the crushing may adhere to the magnetic disk surface,thereby contaminating the magnetic disk surface.

Recently, the abrasive grains used for the burnishing tape are oftendeposited particles (i.e., crystal growth particles) instead of crushedgrains. This is because higher processing accuracy has been demanded inthe burnishing process. In particular, variation in the particlediameter and the shape of the abrasive grains is small in the depositedparticles, which may prevent production of slight scratches on thesurface to be burnished. However, since the deposited particles havesmooth and spherical surfaces as compared to the crushed grains, it isdifficult to stably keep the deposited particles on a support of theburnishing tape. It is therefore considered that the abrasive grains areeasily separated from the burnishing tape during burnishing of themagnetic disk surface.

The invention has been made in view of the aforementioned and an objectthereof is to provide a burnishing tape, a method of producing the sameand a method of burnishing a magnetic disk with which contamination of asurface of the magnetic disk may be prevented during a burnishingprocess of the magnetic disk.

The present inventors have intensively studied to solve the problem andfound that separation or crushing of the abrasive grains may beprevented by a novel burnishing tape for burnishing the magnetic diskand thus contamination of the magnetic disk surface caused by theburnishing tape may be reduced. In particular, a surface of an abrasivegrain layer on the support may be coated with a liquid lubricant layerhaving the thickness of 0.0001 to 10 micrometers to stabilize theshearing force (i.e., the coefficient of dynamic friction) applied tothe burnishing tape. The invention has the following aspects.

(1) A first aspect of the invention is a burnishing tape used to burnisha magnetic disk, the tape including: a support; an abrasive grain layerprovided on the support, the abrasive grain layer containing abrasivegrains; and a liquid lubricant layer with which a surface of theabrasive grain layer is coated.

(2) In a second aspect of the invention, the thickness of the liquidlubricant layer may be in a range of 0.0001 to 10 micrometers.

(3) In a third aspect of the invention, the liquid lubricant layer mayinclude a compound which has a perfluoropolyether structure.

(4) A fourth aspect of the invention is a method of manufacturing aburnishing tape used to burnish a magnetic disk, the method including:kneading and dispersing abrasive grains and a binder to prepare slurry;applying the slurry on a support to form a coating layer; curing thecoating layer to form an abrasive grain layer; and forming a liquidlubricant layer on a surface of the abrasive grain layer.

(5) In a fifth aspect of the invention, the thickness of the liquidlubricant layer may be in a range of 0.0001 to 10 micrometers.

(6) In a sixth aspect of the invention, the liquid lubricant layer mayinclude a compound which has a perfluoropolyether structure.

(7) A seventh aspect of the invention is a method of burnishing amagnetic disk in which an abrasive grain surface of a burnishing tapesupplied to a magnetic disk surface is pressed against and polishes themagnetic disk surface while a magnetic disk is being rotated, the diskincluding, on a nonmagnetic substrate, at least an underlayer, amagnetic layer and a protective layer, wherein the burnishing tapesupplied to the magnetic disk surface is the burnishing tape accordingto any one of above (1) to (3).

(8) A eighth aspect of the invention is a method of burnishing amagnetic disk in which an abrasive grain surface of a burnishing tapesupplied to a magnetic disk surface is pressed against and polishes themagnetic disk surface while a magnetic disk is being rotated, the diskincluding, on a nonmagnetic substrate, at least an underlayer, amagnetic layer and a protective layer, wherein: the burnishing tapesupplied to the magnetic disk surface includes a support and an abrasivegrain layer which contains abrasive grains and is provided on thesupport; and a liquid lubricant is supplied between the support and theabrasive grain layer when the magnetic disk surface is polished by theburnishing tape.

According to the burnishing tape of an aspect of the invention, theliquid lubricant layer may prevent crushing of the abrasive grainsincluded in the abrasive grain layer or removal of the crushed grainsduring burnishing of the magnetic disk. Thus, contamination of themagnetic disk surface caused by the crushed abrasive grains may beprevented. With this configuration, a surface-smoothed magnetic disk,which is sufficiently clean, may be provided.

According to the method of manufacturing a burnishing tape of an aspectof the invention, an excellent burnishing tape may be provided easilyand reliably.

According to the method of burnishing according to an aspect of theinvention, the liquid lubricant layer may prevent crushing of theabrasive grains included in the abrasive grain layer of the burnishingtape or removal of the crushed grains. Thus, contamination of themagnetic disk surface caused by the crushed abrasive grains may beprevented. With this configuration, a surface-smoothed magnetic disk,which is sufficiently clean, may be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of an exemplary burnishingtape according to an embodiment of the invention.

FIG. 2A is a schematic diagram showing an exemplary burnisher in whichthe burnishing tape shown in FIG. 1 is incorporated.

FIG. 2B is a schematic diagram showing an exemplary burnisher in whichthe burnishing tape shown in FIG. 1 is incorporated.

FIG. 3 is a longitudinal cross-sectional view of an exemplary magneticdisk to be burnished in the burnisher shown in FIGS. 2A and 2B.

FIG. 4A is a cross-sectional view of a burnishing tape in which a verythin binder layer is formed on an abrasive grain layer.

FIG. 4B is a cross-sectional view of a related art burnishing tape inwhich abrasive grains are separated or abrasive grains are chipped.

FIG. 4C is a cross-sectional view of an exemplary burnishing tapeaccording to an embodiment of the invention.

FIG. 5 is a schematic configuration diagram showing an exemplarymagnetic recording and reproducing device in which the magnetic diskshown in FIG. 3 is incorporated.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a burnishing tape, a method of manufacturing the same and amethod of burnishing according to embodiments of the invention will bedescribed.

Burnishing Tape

First, a burnishing tape according to an embodiment of the inventionwill be described.

FIG. 1 is a longitudinal cross-sectional view of a burnishing tapeaccording to an embodiment of the invention.

A burnishing tape 1 according to the present embodiment smoothes asurface of a magnetic disk 10 in the following manner: a surface of theburnishing tape 1 is made to slide against a surface of the magneticdisk 10 shown in FIGS. 2A and 2B to polish the surface of the magneticdisk 10 and remove abnormal bumps formed thereon.

The burnishing tape 1 includes a support 2, an abrasive grain layer 3provided on the support 2 and a liquid lubricant layer 4 with which asurface of the abrasive grain layer 3 is coated.

The material of the support 2 is not particularly limited and may bevarious resin materials, such as polyethylene terephthalate.

The abrasive grain layer 3 includes abrasive grains 5 and a binder 6.The surface of the abrasive grain layer 3 has bumps that reflect theshape of the abrasive grains 5.

Examples of the abrasive grains 5 may include particles of chromicoxide, α-alumina, silicon carbide, nonmagnetic iron oxide, diamond,γ-alumina, α,γ-alumina, fused alumina, corundum and synthetic diamond.These substances may be used alone or in combination thereof.

The binder 6 is able to bond the abrasive grains 5 and the support 2 orbond the abrasive grains 5 together. The material of the binder is notparticularly limited and may be a thermosetting resin, thermoplasticresin and photosensitive resin.

Examples of the thermosetting resin may include urea resin, melamineresin, phenol resin, epoxy resin, unsaturated polyester resin, alkydresin and urethane resin.

Examples of the thermoplastic resin may include acrylonitrile styrenebutadiene rubber (ABS) resin, styrene butadiene rubber resin,polybutadiene resin and acrylic rubber-based MBS resin.

Examples of the photosensitive resin may include methacrylic resin,phenol resin, urea resin, melamine resin, polystyrene resin, polyacetalresin, polycarbonate resin and epoxy resin.

These resin materials may be used alone or in combination thereof.

The burnishing tape 1 according to the present embodiment of theinvention is characterized in that the surface of the abrasive grainlayer 3 is coated with the liquid lubricant layer 4.

The thickness of the liquid lubricant layer 4 may preferably be in arange of 0.0001 to 10 micrometers, and more preferably in a range of 0.1to 3 micrometers. With the liquid lubricant layer 4 having the thicknessin this range, separation or crushing of the abrasive grains may beprevented. Even if separation or crushing of the abrasive grains occurs,scattering of the abrasive grain powder may be prevented. With thisconfiguration, adhesion of contaminant that may inhibit the magnetichead from moving in a manner spaced from the magnetic disk in a harddisk device incorporating the magnetic disk may be prevented.

If the thickness of the liquid lubricant layer 4 is smaller than 0.0001micrometers, an effect of preventing the occurrence of the crushedpowder may be impaired. If the thickness of the liquid lubricant layer 4is larger than 10 micrometers, the occurrence of the crushed powder maybe decreased but the liquid lubricant may easily be transferred to thematerial to be polished. As a result, the likelihood of occurrence ofcontamination of the surface of the material to be polished may beincreased.

In the present embodiment, the liquid lubricant layer may preferablyinclude a compound having a perfluoropolyether structure. If the liquidlubricant layer is provided on the surface of the abrasive grain layer,the liquid lubricant may be transferred to the magnetic disk during theburnishing process as described above. Since the compound having aperfluoropolyether structure is generally used as a lubricant to beapplied onto a magnetic disk surface, the likelihood of causing problemsis reduced even if the liquid lubricant of the magnetic tape istransferred to the magnetic disk.

The liquid lubricant layer 4 provided on the surface of the abrasivegrain layer 3 may protect the abrasive grains 5 included in the abrasivegrain layer 3. The liquid lubricant layer 4 may prevent crushing, orremoval of the crushed grains during burnishing of the magnetic disk 10using the burnishing tape 1 may be prevented. The surface of themagnetic disk 10 may be smoothed while preventing contamination of themagnetic disk 10 caused by the crushed grains of the abrasive grains 5.

With the liquid lubricant layer 4 having the thickness in theabove-described range provided on the abrasive grain layer 3, slightscattering of the crushed grains produced by the crushing of theabrasive grains 5 during burnishing of the magnetic disk 10 may bereliably prevented. As a result, it is possible to reliably preventcontaminant (i.e., crushed abrasive grains), which may inhibit themagnetic head from moving in a manner spaced from the magnetic disk,from adhering onto the surface of the magnetic disk 10.

If the thickness of the liquid lubricant layer 4 is smaller than 0.0001micrometers, an effect of preventing the occurrence of the crushing ofabrasive grains 5 or removal of the crushed grains may becomeinsufficient. If the thickness of the coating layer 4 is larger than 10micrometers, the occurrence of crushing of the abrasive grains 5 orremoval of the crushed grains may be reliably prevented. However, thethickness of the lubricant layer 4 covering the surface of abrasivegrains 5 may be excessively large, and thus the function as theburnishing tape may become poor.

Method of Manufacturing Burnishing Tape

Next, a method of manufacturing the burnishing tape according to anembodiment of the invention will be described. The method ofmanufacturing the burnishing tape according to an embodiment of theinvention may include: (1) kneading and dispersing the abrasive grainsand the binder to prepare a slurry; (2) applying the slurry onto thesupport to form a coating layer; (3) making the coating layer cured toform the abrasive grain layer 3; and (4) forming the liquid lubricantlayer 4 on the surface of the abrasive grain layer 3. Hereinafter, eachprocess will be described.

(1) Preparation of Slurry

First, the abrasive grains 5 and the binder 6 are kneaded and dispersedto prepare a slurry.

If the above-described resin is used as the binder 6, the resin materialmay be kneaded and dispersed with the abrasive grains in the form of aprecursor thereof. The precursor of the resin may be a monomer or anoligomer which reacts in various processes in the manufacturing processto yield a target resin.

The slurry may contain a solvent, which helps adjust the viscosity ofthe slurry suitable for application which will be described later.

The solvent is not particularly limited, but may be a ketone-basedsolvent, ester-based solvent, aromatic hydrocarbon solvent,alcohol-based solvent and ether-based solvent.

The content of the abrasive grains 5 in the slurry is preferably in arange of 100 to 400 parts by mass and more preferably 200 to 400 partsby weight with respect to the content of the binder 6 or its precursor.If the content of the abrasive grains 5 is larger than 400 parts bymass, the likelihood of the removal of the abrasive grains 5 in theobtained abrasive grain layer 3 may be increased. If the content of theabrasive grains 5 is smaller than 100 parts by mass, the abrasive grains5 may be buried into the binder 6, and it will become difficult to formbumps that reflect the shape of the abrasive grains 5 on the surface ofthe abrasive grain layer 3.

Any kneader may be used so long as it is usually employed in the methodof manufacturing this kind of burnishing tape.

(2) Formation of Coating Layer

Next, the slurry is applied onto the support 2 to form a coating layer.

The slurry may be coated by any method usually employed in the method ofmanufacturing this kind of burnishing tape. For example, the slurry maybe coated through roll coating or applying.

(3) Curing of Coating Layer

Next, the coating layer formed on the support 2 is made to cure and formthe abrasive grain layer 3.

The method of curing may be selected according to the types of thebinder included in the coating layer and may include heat-treatment orultraviolet irradiation.

In this process, the abrasive grain layer 3 having bumps that reflectthe shape of the abrasive grains 5 may be formed on the surface.

(4) Formation of Lubricant Layer

Next, the liquid lubricant layer 4 is formed on the abrasive grain layer3.

The liquid lubricant layer 4 may be formed on the abrasive grain layer 3by applying a liquid lubricant or a lubricant solution in which alubricant is dissolved in a solvent.

The liquid lubricant layer 4 may be applied by the same methodsdescribed in the process (2).

Conventional burnishing tapes are usually manufactured in the processes(1) to (3) among the described processes (1) to (4). In this method ofmanufacturing, the abrasive grains are kneaded with the binder in theprocess of (1) so that the surface of the abrasive grain is covered withthe binder. If the abrasive grain is made to cure as an abrasive grainlayer on the support, the surface of the abrasive grain layer isslightly coated with a solid binder. The thickness of the coating layerof the binder, however, is very small and may be as thin as less than0.01 micrometers according to analysis of the present inventors. This isbecause the binder covering an upper surface of the abrasive grains 5 asshown in FIG. 4A will gather on the support 2 due to self-weight at thetime of curing, and the thickness of the binder 6 on the surface 5 c ofthe abrasive grains 5 becomes very thin.

If the conventional burnishing tape including the abrasive grain layer 3is used to burnish the magnetic disk, as shown in FIG. 4B, the abrasivegrains 5 contained in the burnishing tape may be separated to producetraces 8 of separation or produce crushed abrasive grains 7. Abrasivegrains separated or crushed are removed from the burnishing tape andcontaminate the magnetic disk surface during burnishing.

In order to prevent the occurrence of such a phenomenon, as shown inFIG. 4C, the invention includes the liquid lubricant layer 4 provided onthe surface of the abrasive grain layer 3 of the conventional burnishingtape prepared in the processes of (1) to (3). With this configuration,the shearing force applied to the burnishing tape 1 of an embodiment ofthe invention during burnishing may be stabilized. Thus, the separationor crushing of the abrasive grains 5 which constitute the abrasive grainlayer 3 of the burnishing tape may be prevented. As a result,contamination of the magnetic disk surface during burnishing may beprevented.

Burnishing

Next, a method of burnishing according to an embodiment of the inventionwill be described.

FIGS. 2A and 2B are schematic diagrams of an exemplary burnisher used ina burnishing process of the invention. FIG. 3 is a longitudinalcross-sectional view of an exemplary magnetic disk to be burnishedaccording to an embodiment of the invention.

In the burnishing of the invention, the polishing surface S (i.e., thesurface of the liquid lubricant layer) is pressed against a surface ofthe magnetic disk 10 to make them slide against each other to polish thesurface of magnetic disk 10 and remove the abnormal bumps on thesurface.

First, an exemplary magnetic disk to which the burnishing of theinvention is applied will be described with reference to FIG. 3.

The magnetic disk 10 shown in FIG. 3 schematically includes anunderlayer 12, an intermediate layer 13, a magnetic layer 14 and aprotective layer 15 laminated successively on both main surfaces of anonmagnetic substrate 11. A lubricant layer 16 is provided on top ofthese layers.

The material of the nonmagnetic substrate 11 is not particularly limitedand may include a nonmagnetic aluminum alloy material and glass materialusually employed as a material for the magnetic disk 10. Examples of theglass material may include usual soda glass, alumino silicate-basedglass and amorphous glass. Examples of the aluminum alloy material mayinclude an Al—Mg alloy consisting mainly of Al. Alternatively, thenonmagnetic substrate 11 may be formed of any nonmagnetic substances,such as silicon, titanium and ceramic, and various resin materials.

The nonmagnetic substrate 11 may contain an substrate of aluminum orglass and a surface layer in which one or more layers consisting of NiP,NiP alloy or another alloy are formed on the substrate of aluminum orglass by plating, sputtering or other processes.

The underlayer 12 may be formed of Cr or a Cr alloy consisting of Cr andone or more of Ti, Mo, Al, Ta, W, Ni, B, Si, Mn and V.

When the underlayer 12 is formed as a multilayered nonmagneticunderlayer, at least one of layers constituting the nonmagneticunderlayer may be formed of Cr or the above-described Cr alloy.

The nonmagnetic underlayer may consist of a NiAl-based alloy, aRuAl-based alloy or a Cr alloy (an alloy which consists of Cr and one ormore of Ti, Mo, Al, Ta, W, Ni, B, Si and V).

If a multilayered nonmagnetic underlayer is used, at least one of thelayers constituting the nonmagnetic underlayer may consist of aNiAl-based alloy, RuAl-based alloy or the above-described Cr alloy.

The intermediate layer 13 preferably uses a nonmagnetic material formedof a Co alloy consisting mainly of Co and having an hcp structure from aviewpoint of promoting epitaxial growth of the Co alloy. Examples of theCo alloy may include a Co—Cr-based alloy, Co—Cr—Ru-based alloy,Co—Cr—Ta-based alloy and Co—Cr—Zr-based alloy. The intermediate layer 13may preferably include one or more of these Co-based alloys.

The magnetic layer 14 preferably uses a material formed of a Co alloyconsisting mainly of Co and having an hcp structure. Examples of the Coalloy may include a Co—Cr—Ta-based alloy, Co—Cr—Pt-based alloy,Co—Cr—Pt—Ta-based alloy, Co—Cr—Pt—B-based and Co—Cr—Pt—B—Cu-based alloy.The magnetic layer 14 may preferably include one or more of theseCo-based alloys. The magnetic disk according to the present embodimentmay also have a layered structure consisting or two or more magneticlayers.

The protective layer 15 may be formed of a carbon-based material, suchas CVD carbon, amorphous carbon, hydrogen-containing carbon,nitrogen-containing carbon and fluorine-containing carbon, which areformed by plasma CVD, and ceramic-based materials, such as silica andzirconia. Among these, hard and fine CVD carbon is suitably used fromthe viewpoint of economical efficiency and productivity. The thicknessof the protective layer 15 may preferably be 0 to 150 angstroms (1 to 15nm), and more preferably be 20 to 60 angstroms (2 to 6 nm). If theprotective layer 15 is too thin, durability may become insufficient. Ifthe protective layer 15 is too thick, loss during recording andreproduction may become large.

The lubricant layer 16 which is the top layer may be formed of amaterial containing a polymer of polymerized unsaturatedgroup-containing perfluoropolyether compound. The polymerizedunsaturated group-containing perfluoropolyether compound may be acompound which includes an organic group having a polymerizableunsaturated bonding at least one end of perfluoropolyether, which is amain chain.

The magnetic disk to be burnished by the method according to theinvention may be an in-plane magnetic disk or a perpendicular magneticdisk.

Next, an exemplary burnisher used to burnish in the invention will bedescribed with reference to FIGS. 2A and 2B.

A burnisher 20 shown in FIGS. 2A and 2B includes a magnetic disk rotarydrive mechanism 21, burnishing tapes 1 a and 1 b, a burnishing taperunning system 22 and a burnishing tape pressing device 23.

The magnetic disk rotary drive mechanism 21 includes a spindle 24 whichis driven to rotate by an unillustrated spindle motor, and a magneticdisk holding mechanism 25 attached to the center of the spindle 24. Thecentral portion of the magnetic disk 10 is secured to the magnetic diskholding mechanism 25, which holds the magnetic disk 10. When the spindle24 is driven to rotate with the magnetic disk 10 held by the magneticdisk holding mechanism 25, the magnetic disk 10 is rotated according tothe rotational direction and the rotational rate of the spindle 24.

The magnetic disk rotary drive mechanism 21 is configured to rotate themagnetic disk 10 in a rotational direction (the direction of arrow r inFIGS. 2A and 2B) such that the scanning direction of a track of themagnetic disk 10 which is rotated is opposite to the running directionof a first burnishing tape 1 a which is moved between a first guide roll26 and a second guide roll 27 (i.e., the direction of arrow Ra in FIGS.2A and 2B), which will be described later, and is opposite to therunning direction of a second burnishing tape 1 b which is moved betweena fifth guide roll 30 and a sixth guide roll 31 (i.e., the arrow Rbdirection in FIGS. 2A and 2B).

The burnishing tapes 1 a and 1 b are elongated tapes fabricated in themethod of manufacturing of the burnishing tape described above.

A burnisher 20 includes a first burnishing tape 1 a and a secondburnishing tape 1 b. The first burnishing tape 1 a is moved such that apolishing surface S thereof is moved opposing a first main surface 10 aof the magnetic disk 10. The second burnishing tape 1 b is moved suchthat a polishing surface S thereof is moved opposing a second mainsurface 10 b of the magnetic disk 10.

The burnishing tape running system 22 has a first burnishing taperunning system 22 a and a second burnishing tape running system 22 b,and the magnetic disk 10 is disposed between the burnishing tape runningsystem 22 a and the second burnishing tape running system 22 b. Thefirst burnishing tape running system 22 a includes an unillustratedsupply roll, a take-up roll and first to fourth guide rolls 26 to 29disposed below the supply roll and the take-up roll.

The first to fourth guide rolls 26 to 29 are disposed such that eachrotation axis thereof is substantially parallel to a first main surface10 a of the magnetic disk 10 and rotation axes thereof are mutuallysubstantially parallel to each other. The first and second guide rolls26 and 27 are disposed such that their distances from the first mainsurface 10 a of the magnetic disk 10 are substantially equal to eachother. The third and fourth guide rolls 28 and 29 are disposed such thattheir distances from the first main surface 10 a of the magnetic disk 10are substantially equal to each other at a position further apart fromthe magnetic disk 10 than the first and second guide rolls 26 and 27

In the thus-configured first burnishing tape running system 22 a, theelongated first burnishing tape 1 a is sequentially fed out from thesupply roll. The first burnishing tape 1 a fed from the supply roll ismoved along a substantially U-shaped running route while being guided bythe first to fourth guide rolls 26 to 29, and then taken up by thetake-up roll. Here, the polishing surface S of the first burnishing tape1 a opposes the first main surface 10 a of the magnetic disk 10 whenmoving between the first and second guide rolls 26 and 27.

The second burnishing tape running system 22 b includes an unillustratedsupply roll, a take-up roll and fifth to eighth guide rolls 30 to 33.The fifth to eighth guide rolls 30 to 33 are disposed symmetrically withthe first to fourth guide rolls 26 to 29 at both sides of the magneticdisk 10.

In the thus-configured second burnishing tape running system 22 b, anelongated second burnishing tape 1 b is sequentially fed from the supplyroll. The second burnishing tape 1 b fed from the supply roll is movedalong a substantially U-shaped running route while being guided by thefifth to eighth guide rolls 30 to 33 and then taken up by the take-uproll. Here, the polishing surface S of the second burnishing tape 1 bopposes the second main surface 10 b of the magnetic disk 10 when movingbetween the fifth and sixth guide rolls 30 and 31.

The burnishing tape pressing device 23 includes a first burnishing tapepressing device 23 a and a second burnishing tape pressing device 23 b.The first burnishing tape pressing device 23 a presses the firstburnishing tape 1 a which is moved between the first and second guiderolls 26 and 27 to bring into contact with (i.e., dab against) the firstmain surface 10 a of the magnetic disk 10. The second burnishing tapepressing device 23 b presses the second burnishing tape 1 b which ismoved between the fifth and sixth guide rolls 30 and 31 to bring intocontact with (i.e., dab against) the second main surface 10 b of themagnetic disk 10.

In a state in which the magnetic disk 10 is driven to rotate in thedirection of arrow r shown in FIGS. 2A and 2B by the magnetic diskrotary drive mechanism 21, if the first burnishing tape 1 a movingbetween the first and second guide rolls 26 and 27 is pressed againstthe first main surface 10 a of the magnetic disk 10 by the firstburnishing tape pressing device 23 a, and the second burnishing tape 1 bmoving between the fifth and sixth guide rolls 30 and 31 is pressedagainst the second main surface 10 b of the magnetic disk 10 by thesecond burnishing tape pressing device 23 b, the polishing surface S ofthe first burnishing tape 1 a is made to slide against the first mainsurface 10 a and the polishing surface S of the second burnishing tape 1a is made to slide against the second main surface 10 b. In this manner,both main the surfaces 10 a and 10 b of the magnetic disk 10 arepolished by the burnishing tapes 1 a and 1 b so that bumps on both themain surfaces 10 a and 10 b are removed to provide smooth main surfaces.Here, in the burnisher 20 of the present embodiment, since unusedburnishing tapes 1 a and 1 b are sequentially fed from the supply roll,used for polishing and then taken up to the take-up roll, unusedburnishing tapes 1 a and 1 b are always supplied to each main surface ofthe magnetic disk 10. Thus, each main surface 10 a and 10 b of themagnetic disk 10 may be polished efficiently.

The first and second burnishing tape pressing devices 23 a and 23 b arepreferably formed of a material having flexibility at an area to be incontact with the burnishing tapes 1 a and 1 b. With this configuration,the polishing surfaces S of the burnishing tapes 1 a and 1 b may bepressed against the surfaces of the magnetic disk 10 sufficiently closeto each other so as to efficiently polish the surface of the magneticdisk 10. Exemplary first and second burnishing tape pressing devices 23a and 23 b may be, for example, a pad consisting of resin or textile ora device having a pressing member, such as a rubber roller, which willbe made to abut a back surface of the burnishing tape so as to press theburnishing tapes 1 a and 1 b against the magnetic disk 10.

In the burnisher 20 of the present embodiment, the first and secondburnishing tape pressing devices 23 a and 23 b each include metal blocks34 and 35, pads 36 and 37 attached to one side surface of the metalblocks 34 and 35 and a driving means (not shown) which makes the metalblocks 34 and 35 reciprocate in a horizontal direction (i.e., adirection perpendicular to each main surface of the magnetic disk,indicated by arrows F1 and F2 in FIGS. 2A and 2B).

In such burnishing tape pressing devices 23 a and 23 b, as shown in FIG.2A, when the driving means makes the metal blocks 34 and 35 move in thedirection of arrow F1 with the pads 36 and 37 being spaced apart fromthe burnishing tapes 1 a and 1 b (i.e., a stand-by state), the pads 36and 37 abut the back surface of the burnishing tapes 1 a and 1 b andpress the burnishing tapes 1 a and 1 b against the magnetic disk 10. Asa result, as shown in FIG. 2B, the polishing surfaces S of theburnishing tapes 1 a and 1 b are brought into contact with the mainsurfaces of the magnetic disk 10. In this state, when the driving meansmakes the metal blocks 34 and 35 move in the direction indicated by thearrow F2, the burnishing tapes 1 a and 1 b move apart from the magneticdisk 10, and further, the pads 36 and 37 move apart from the burnishingtapes 1 a and 1 b, and the driving means returns to its stand-by state.

Next, an operation of the burnisher 20 will be described.

The first burnishing tape 1 a is placed on the first burnishing taperunning system 22 a and the second burnishing tape 1 b is placed on thesecond burnishing tape running system 22 b.

The magnetic disk holding mechanism 25 is mounted on and held by themagnetic disk 10.

As shown in FIG. 2A, in the initial state of the burnisher 20, each ofthe pads 36 and 37 of the first and second burnishing tape pressingdevices 23 a and 23 b is spaced apart from the burnishing tapes 1 a and1 b (i.e., stand-by state).

Next, when operation of each part is turned on, the magnetic diskrotating drive mechanism 21 drives the magnetic disk 10 to rotate in thedirection of arrow r shown in FIG. 4A. Each supply roll sequentiallyfeeds the first and second burnishing tapes 1 a and 1 b. The fed firstburnishing tape 1 a is moved along the substantially U-shaped runningroute while being guided by the first to fourth guide rolls 26 to 29,and then taken up by the take-up roll. The fed second burnishing tape 1b is moved along the substantially U-shaped running route while beingguided by the fifth to eighth guide rolls 30 to 33, and then taken up bythe take-up roll.

The polishing surface S of the first burnishing tape 1 a which is movedbetween first and second guide rolls 26 and 27 opposes the first mainsurface 10 a of the magnetic disk 10 and is moved in a directionopposite the scanning direction of the track of the magnetic disk 10.

The polishing surface S of the second burnishing tape 1 b which is movedbetween the fifth guide roll 30 and the sixth guide roll 31 opposes thesecond main surface 10 b of the magnetic disk 10 and is moved in adirection opposite the scanning direction of the track of the magneticdisk 10.

Next, the first burnishing tape pressing device 23 a presses the firstburnishing tape 1 a moving between the first and second guide rolls 26and 27 against the first main surface 10 a of the magnetic disk 10 andbrings the polishing surface S of the burnishing tape 1 a in contactwith (i.e., dab against) the first main surface 10 a. The secondburnishing tape pressing device 23 b presses the second burnishing tape1 a which is moved between the fifth and sixth guide rolls 26 and 27against the second main surface 10 b of the magnetic disk 10 and bringsthe polishing surface S of the burnishing tape 1 b in contact with(i.e., dab against) the second main surface 10 b.

When the polishing surface S of the moving first burnishing tape 1 a ispressed against the first main surface 10 a of the magnetic disk 10while the magnetic disk 10 being driven to rotate in the direction ofarrow r in FIGS. 2A and 2B and the polishing surface S of the movingsecond burnishing tape 1 b is pressed against the second main surface 10b of the magnetic disk 10, the polishing surface S of the firstburnishing tape 1 a is made to slide against the first main surface 10 aand the polishing surface S of the second burnishing tape 1 a is made toslide against the second main surface 10 b. In this manner, both themain surfaces 10 a and 10 b of the magnetic disk 10 are polished by theburnishing tapes 1 a and 1 b so that bumps on both the main surfaces 10a and 10 b are removed to provide smooth main surfaces.

Since the lubricant layer 4 having the above-described structure isprovided in the burnishing tape 1, the occurrence of crushing of theabrasive grains 5 included in the abrasive grain layer 3 or removal ofthe crushed grains may be prevented. In this manner, the surface of themagnetic disk 10 may be smoothed while contamination of the magneticdisk 10 caused by the crushed grains is prevented. Even if thethus-processed magnetic disk 10 is incorporated in a magnetic recordingand reproducing device (i.e., a hard disk device) in which the distancebetween the magnetic head and the magnetic disk 10 is very small,collision between the magnetic head and the magnetic disk 10 may beprevented to provide desired operating characteristics.

The burnishing tape 1 used in the present embodiment includes theabrasive grain layer 3 on the support 2 and the surface of the abrasivegrain layer 3 is covered by the liquid lubricant layer 4 having thethickness of 0.01 to 10 micrometers. In another embodiment, however, aburnishing tape having no liquid lubricant layer may alternatively besupplied to the burnisher as a burnishing tape 1 and a liquid lubricantmay be dropped onto the burnishing surface from above the burnishingtape during burnishing. The dropping amount of the liquid lubricantshould be carefully determined. If the dropping amount of the liquidlubricant is too large, the surface of the magnetic disk may becontaminated with the liquid lubricant.

The burnished magnetic disk according to the invention is then processedat a final inspection process (i.e., a tester) and is incorporated inthe magnetic recording and reproducing device (i.e., the hard diskdevice).

In the other embodiment, as a method of burnishing a magnetic disk,which includes a step of polishing a surface of a magnetic diskcomprising at least an underlayer, a magnetic layer and a protectivelayer on a nonmagnetic substrate, after pressing an abrasive grainsurface of a burnishing tapes 1 a and 1 b supplied to the magnetic disksurface, while the magnetic disk is rotated, the burnishing tapes 1 aand 1 b supplied to the magnetic disk surface includes a support 2 andan abrasive grain layer 3 which contains abrasive grains and is providedon the support 2; and the method of burnishing a magnetic disk furtherincludes a step of supplying a liquid lubricant between the support 1and the abrasive grain layer when the magnetic disk surface is polishedby the burnishing tape 1.

When implementing this method, since viscosity of a 100% lubricant isexcessively high, the lubricant may preferably be diluted with asolvent. The concentration of the lubricant may preferably be 0.01% byvolume and thus the dripping amount of the diluted solution maypreferably be about 0.01 to 1 cc per second. A fluorine-based solventmay be used as the solvent.

As described above, contamination of the magnetic disk surface may beprevented, which has the same effect as the burnishing process in whicha lubricant is supplied before the burnishing process and the resultingburnishing tape 1 having the lubricant layer 4 is used during theburnishing, as described previously.

Magnetic Recording and Reproducing Device

Next, an example of a magnetic recording and reproducing device in whichthe magnetic disk processed by the burnishing process of the inventionis incorporated will be described.

FIG. 5 is a schematic configuration diagram of an exemplary magneticrecording and reproducing device.

The magnetic recording and reproducing device 80 includes a burnishedmagnetic disk 10 according to the embodiment of the invention, a mediumdriving section 81 which drives to rotate the magnetic disk 10, amagnetic head 82 which records information in the magnetic disk 10 andreproduces the recorded information, a head driving section 83 whichdrives a magnetic head 27 to move relatively with the magnetic disk 10and a recording and reproducing signal processing system 84. Therecording and reproducing signal processing system 84 is configured toprocess input data, transmit obtained recording signals to the magnetichead 82, process reproducing signals from the magnetic head 82 andoutput obtained data.

The surface of the magnetic disk 10 of the magnetic recording andreproducing device 80 is fairly smooth due to the burnishing process ofthe invention and is thus very clean. Accordingly, even if the distancebetween the magnetic head 82 and the magnetic disk 10 is very small,collision between the magnetic head 82 and the magnetic disk 10 may beprevented to provide high recording density and reliability.

Example

An Example for demonstrating the invention will be given below forillustrative purposes only. The invention is not limited to the Example.

Fabrication of Magnetic Disk

A washed glass substrate (manufactured by HOYA Corporation, 2.5 inchesin outer diameter) is placed in a film forming chamber of a DC magnetronsputtering apparatus (C-3010 manufactured by Canon ANELVA Corporation).A vacuum is formed in film forming chamber so that the ultimate vacuumbecomes 1×10⁻⁵ Pa. On this glass substrate, a target of 89Co-4Zr-7Nb (Cocontent 89 at %, Zr content 4 at % and Nb content 7 at %) is used toform a 100-nm-thick underlayer by sputtering at the substratetemperature of 100° C. or less.

The glass substrate is then heated to 200° C., and a 5-nm-thickintermediate layer is formed on the underlayer using a 65Co-30Cr-5Btarget. Then, a 25-nm-thick magnetic layer is formed using a61Co-20Cr-17Pt-2B target. In this sputtering process, a layer is formedusing argon as the process gas with the pressure inside the film formingchamber being 0.5 Pa.

A 5-nm-thick protective film layer is formed on the magnetic layer bythe plasma CVD.

A lubricant layer consisting of perfluoropolyether is formed by dipping.In this manner, a magnetic disk having various layers formed on theglass substrate is obtained.

Each of the thus-obtained 1000 magnetic disks is placed in a tapeburnisher 20 as shown in FIGS. 2A and 2B to polish the surface thereof.

A burnishing tape is fabricated in the following manner. Aluminaparticles (i.e., crystal growth particles) having an average particlediameter of 0.5 micrometers are made to adhere to a polyethyleneterephthalate film by epoxy resin in a single particle layer. Then, aperfluoropolyether liquid lubricant layer is applied to the aluminaparticle surface to the thickness of about 1 micrometer.

The thickness of the layer formed by using the epoxy resin is about 0.3micrometers from the surface of the film. The thickness of the epoxyresin layer is about 0.2 micrometers from the upper surfaces of thealumina particles. The burnishing tape is pressed against the magneticdisk surface at the pressure of 98 mN. The magnetic disk is driven torotate at 300 rpm. The burnishing tape is fed at the rate of 10 mm persecond. In this manner, the burnishing is continued for 5 seconds.

Evaluation of Burnishing Tape

Each of the thus-obtained 1000 magnetic disks is placed in a tester(i.e., a surface test device) and the disk surface of each magnetic diskis examined. As a result, separated alumina grains are observed toadhere into the surfaces of three magnetic disks.

Comparative Example

Each of 1000 magnetic disks are fabricated and subject to a tapeburnishing process both under the same condition as that in the Example.In this example, the burnishing tape, which is the same as that used inthe Example except that no liquid lubricant layer is provided, is used.

Each of the thus-fabricated 1000 magnetic disks is examined under thesame condition as that of the Example, and the separated aluminaparticles are observed to adhere into the surfaces of 55 disks.

According to the comparison result, it is found that the method ofExample of the invention has significant effects. In particular, thenumber of the alumina particles adhering into the surface of themagnetic disks is only three out of 1000 after burnishing the magneticdisks, while the number of the alumina particles adhering into thesurface of the magnetic disks is as many as 55 out of 1000 in theComparative Example in which no liquid lubricant layer is provided.

The burnishing tape according to an embodiment of the invention maysmooth the surface of the magnetic disk while magnetic diskcontamination caused by crushed abrasive grains is prevented. Thus, theburnishing tape is suited to burnish the magnetic disk which is to beapplied to a hard disk device in which the distance between the magnetichead and the magnetic disk is very small.

It is apparent that the present invention is not limited to the aboveExample, but may be modified and changed without departing from thescope and spirit of the invention.

1. A burnishing tape used to burnish a magnetic disk, the tape comprising: a support; an abrasive grain layer, which comprises abrasive grains and is provided on the support; and a liquid lubricant layer with which a surface of the abrasive grain layer is coated.
 2. The burnishing tape according to claim 1, wherein the thickness of the liquid lubricant layer is in a range of 0.0001 to 10 micrometers.
 3. The burnishing tape according to claim 1, wherein the liquid lubricant layer comprises a compound which has a perfluoropolyether structure.
 4. The burnishing tape according to claim 2, wherein the liquid lubricant layer comprises a compound which has a perfluoropolyether structure.
 5. A method of manufacturing of a burnishing tape used to burnish a magnetic disk, the method comprising: kneading and dispersing abrasive grains and a binder to prepare a slurry; applying the slurry on a support to form a coating layer; curing the coating layer to form an abrasive grain layer; and forming a liquid lubricant layer on a surface of the abrasive grain layer.
 6. The method of manufacturing of the burnishing tape according to claim 5, wherein the thickness of the liquid lubricant layer is in a range of 0.0001 to 10 micrometers.
 7. The method of manufacturing the burnishing tape according to claim 5, wherein the liquid lubricant layer comprises a compound which has a perfluoropolyether structure.
 8. The method of manufacturing the burnishing tape according to claim 6, wherein the liquid lubricant layer comprises a compound which has a perfluoropolyether structure.
 9. A method of burnishing a magnetic disk, which comprises a step of polishing a surface of a magnetic disk comprising at least an underlayer, a magnetic layer and a protective layer on a nonmagnetic substrate, after pressing an abrasive grain surface of a burnishing tape supplied to the magnetic disk surface, while the magnetic disk is rotated, wherein the burnishing tape supplied to the magnetic disk surface is the burnishing tape according to claim
 1. 10. A method of burnishing a magnetic disk, which comprises a step of polishing a surface of a magnetic disk comprising at least an underlayer, a magnetic layer and a protective layer on a nonmagnetic substrate, after pressing an abrasive grain surface of a burnishing tape supplied to the magnetic disk surface, while the magnetic disk is rotated, wherein the burnishing tape supplied to the magnetic disk surface is the burnishing tape according to claim
 2. 11. A method of burnishing a magnetic disk, which comprises a step of polishing a surface of a magnetic disk comprising at least an underlayer, a magnetic layer and a protective layer on a nonmagnetic substrate, after pressing an abrasive grain surface of a burnishing tape supplied to the magnetic disk surface, while the magnetic disk is rotated, wherein the burnishing tape supplied to the magnetic disk surface is the burnishing tape according to claim
 3. 12. A method of burnishing a magnetic disk, which comprises a step of polishing a surface of a magnetic disk comprising at least an underlayer, a magnetic layer and a protective layer on a nonmagnetic substrate, after pressing an abrasive grain surface of a burnishing tape supplied to the magnetic disk surface, while the magnetic disk is rotated, wherein: the burnishing tape supplied to the magnetic disk surface comprises a support and an abrasive grain layer which contains abrasive grains and is provided on the support; and a liquid lubricant is supplied between the support and the abrasive grain layer when the magnetic disk surface is polished by the burnishing tape. 